Individual Variation & Genetics in calorie intake and weight gain/loss

Nutrition Q&A [Moderated]
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Hi Jordan,

I wondered how much individual variation there is and how much genetics may play a factor in terms of calorie intake and weight gain/loss?

I was recently telling a colleague that I am 65kg and eat almost as much as my husband who is 105kg. He said this was ‘impossible’ given our weight difference. He asserted that given my weight I must eat around X calories to maintain this.

I do more aerobic physical activity than my husband, but I also appear to have ‘lean’ genetics and my husband tends to hold onto weight like the rest of his family who are all overweight.

My colleague is an advocate of Herman Pontzer’s work and I know that he asserts physical activity does not have a great influence on weight loss. I wonder if there are limitations to Pontzer’s findings? Is it possible there is more ‘nuance’ to this as you might say?

In the last two years I have increased my physical activity levels, increased my food consumption and lost 7kg. If I didn’t increase my calorie intake I would have lost more weight. I was also a competitive swimmer, swimming up to 20hrs/wk when I was younger and weighed 55kg and ate vast quantities of food, much more than I eat now. Am I delusional??

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There are a great number of ways genetics influence weight management and body composition:

  1. The resistance or sensitivity to gaining weight (predominantly fat) from overfeeding
  2. The resistance or sensitivity to losing weight (predominantly fat) from energy restriction
  3. the ratio of muscle mass/fat gained or loss with weight change
  4. compensatory behaviors- conscious and subconscious- in response to weight gain or loss, food environment, etc.
  5. LBM amount
  6. Hormone levels related to energy liberation
  7. and many more As far as if you and your husband eat similar amounts of energy, on average, to maintain weight, I would be skeptical of that. LBM is the biggest predictor of energy expenditure and I would not expect you two to have similar TDEE’s.
1 Like
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Thanks Jordan.

That’s interesting. Would you say there is also variation in resistance or sensitivity to weight loss with physical activity?

You are right that overall my husband would eat more energy than me. However given our respective sizes you would assume I would eat much less than him or he would eat much more than me. But the difference in our energy consumption does not I think directly correlate with the difference in our size because of all the factors you mention above.

I wonder about these things because I observe people who find it difficult to lose weight in spite of not eating a great deal. I know that there’s a level of subjectivity and perhaps lack of education in many when it comes to accurately measuring how much we eat, and that this can often lead to under-reporting of calorie consumption. But if you put aside those that underestimate calorie consumption and those that are unable to adhere to a reduced energy intake (for all the reasons you describe in your obesity talks) it seems like there are people that do all the right things but are resistant to losing weight due to their genetics. Is that fair to say?

I’ve heard health professionals smirk at these people who find it difficult to lose weight and insinuate that they must be lying about what they are eating which can be highly stigmatising.